The airspace through which aircraft travel is divided into three-dimensional regional zones or sectors known as air traffic control (ATC) sectors. The boundaries of each ATC sector are defined laterally by latitudinal and longitudinal coordinates, and vertically by specifically designated lower and upper altitude limits. The boundaries between ATC sectors may be horizontal, vertical, or both. In addition to the boundaries, each ATC sector is typically assigned a set of permanent communication frequencies in both the very-high frequency (VHF) range and the ultra-high frequency (UHF) range. Air traffic controllers (or just “controllers”) use these frequencies to maintain voice contact with aircraft crews. In this manner, air traffic controllers maintain control over the aircraft with respect to ATC directions and clearances.
To ensure adequate separation between aircraft, controllers should be aware of all aircraft that are in their ATC sector and know when aircraft enter or leave their ATC sector. Aircraft may enter an ATC sector only with the permission of the controller that controls that ATC sector. Before an aircraft passes from one ATC sector to the next, a controller in the current ATC sector will typically direct the pilot to change the frequency of the aircraft communications radio from the current sector frequency to the frequency of the next ATC sector. The pilot then manually tunes the aircraft communications radio to that frequency, and initiates the voice communication with the controller in the next ATC sector. Although the present system and method is generally safe and reliable, as will now be described, it does suffer certain drawbacks.
The above-described ATC sector frequency changing activities are performed by the pilot each time the aircraft travels between ATC sectors, potentially distracting the pilot. Additionally, pilots presently do not have an automated means of knowing where the ATC sector boundaries are located; thus the notice to change ATC sector frequencies can seemingly be unexpected and random in nature. For jet aircraft, these ATC sector frequency changes can take place, on average, up to nine times per flight hour.
Moreover, ATC sector coverage depends on the type of equipment installed at the ATC station. For example, a simple ATC sector at an airfield may extend in a 10 mile radius around the airfield, and to a height of 10,000 feet above the airfield. Other ATC stations equipped with long range radar have the capability, at higher altitudes, to see aircraft within 200 nautical miles of the radar antenna. Of course, the communication range of an aircraft is limited by the capacity of its communications radio. For example, the range of typical Class 3 and 5 communications radios is up to about 200 nautical miles, whereas the range of typical Class 4 and 6 communications radios is only up to about 100 nautical miles. It may thus be readily understood that the two-way communication between a controller and a pilot is limited to the minimum of the respective communication equipment ranges. This may place an additional constraint upon determining when an aircraft will pass outside the range of the current ATC sector, which may be well before the actual boundary of the ATC sector. In some instances, a pilot may not realize when the aircraft is approaching the range of the aircraft communications radio and may not initiate an appropriate ATC sector frequency change in a timely manner.
Furthermore, not all stations in an ATC sector operate 24 hours a day and/or throughout the year. The daily working hours may vary based on the aircraft traffic and the available personnel. For example, stations in some ATC sectors may operate from 06:00 to 22:00. Prior to filing a flight plan, a pilot is expected to know the operational hours and/or days of the ATC stations with which the pilot may communicate. If not, the pilot may end up flying the aircraft into a non-operational ATC sector or an uncontrolled sector, where the pilot cannot communicate with an ATC communication station.
Methods are therefore needed in order to overcome these and other limitations of the prior art. What is needed is an improved, efficient, and intuitive method for ATC switchover operation. Methods are needed to improve a pilot's situational awareness with respect to available ATC stations. Additionally methods are needed to help a pilot in planning the flight path with respect to available and unavailable ATC sectors Further, methods are needed to suggest modifications to planned routes in flight plans to achieve maximum ATC coverage during the flight.